1. Field of the Invention
This invention relates to a collector ring for a center pivot irrigation machine which allows the mounting of a communication device above the span structure and/or includes a monitoring device which monitors the angle or rotation of the span structure with respect to the fixed center pivot structure.
2. Description of the Related Art
Due to increasing fuel and labor costs, the demand for remote control of mechanized irrigation systems such as center pivot irrigation systems is increasing. In those situations where the irrigation system includes remote control capabilities, it is necessary for an antenna or other communication device to be mounted at the fixed center pivot structure. One of the limitations associated with the remote control of mechanized irrigation systems is the height at which the antenna or communication device can be mounted at the center pivot structure. The height of the communication device is directly related to the quality and range of the telemetry used for remote communications. The higher the communication device is mounted, the better the signal quality and signal range. Because center pivot irrigation systems move in a full-circle rotation, communication devices such as antennas are typically mounted below the full-circle rotating span structure, which limits the mounting height of the antenna or communication device due to the height of the span structure. Communication devices such as antennas can be mounted above the span structure by electrically connecting and routing the signal wires through the slip rings of the conventional collector ring at the center pivot structure although the degradation of the signal quality is severe due to the electrical connection and routing of the signal wires through the slip rings.
FIG. 1 illustrates a prior art internal collector ring assembly commonly associated with a center pivot irrigation system. The swivel and span structure 1 rotates in a full circle with respect to the stationary center pivot structure 2. Electrical signal wires from the control panel mounted on the pivot structure are routed through the inside of the swivel 1, up the inside of the mounting tube 3 and into the collector ring assembly 4 where the signal wires are electrically connected to the slip rings so as to be routed therethrough. The mounting tube 3 is fixed to the center pivot structure and does not rotate with the swivel and span assembly 1. Control bar 5 rotates with the swivel and span structure 1 and rotates the shaft of a decoder, angle sensor or resolver mounted to the mounting tube inside the collector ring assembly, thereby providing position signals to the control panel of the system.
The structure of FIG. 1 is more specifically shown in FIG. 2 wherein a position encoder 6 is mounted on the upper end of the mounting tube 3 which is mounted to the stationary center pivot structure 2. In FIG. 2, the mounting tube 3 does not rotate. The control bar 5 is connected to the span structure 1 and rotates with the span structure thereby causing the rotation of the rest of the collector ring assembly 4. The position encoder bar 7 is mounted to the collector ring assembly 4 which is mounted to the control bar 5. As the position encoder bar 7 rotates with the span structure 1, it rotates the arm of the position encoder 6, thereby providing position information back to the control panel mounted on the center pivot structure. It is important to note that the wires 8, which extend from the pivot control panel mounted on the stationary center pivot structure, extend upwardly through the mounting tube 3 and do not rotate with the swivel and span structure. The wires 8 are connected to the slip rings of the collector ring to supply electrical power thereto. Wires are connected to the wipers or brushes 9 and extend outwardly from the collector ring assembly 4 out onto the span structure, thereby allowing the full circular rotation of the swivel and span structure without binding or twisting the wires 8 extending from the control panel. The prior art structure of FIGS. 1 and 2 does not permit the use of a communication device such as an antenna positioned above the span structure since the collector ring assembly 4 rotates with the span structure.
Certain prior art devices also have external collector ring and position encoders but the same likewise do not permit the positioning of an antenna above the span structure.